of state john kerry boarded an air force jet and headed to ukraine. he is expected to meet with the new leadership of kiev testimony. trying to rally international allies to bring pressure on russia to stand back from an intense standoff. ukraine's envoy to the u.n. says russia has flooded crimea with 16,000 troops in the past week. russia says it's protecting the russian people in ukraine, and its own military bases there. the president obama said russia must respect ukraine sovereignty, and said russia is on the wrong side of history. >> over time, this will be costly proposition for russia. and now is the time for them to consider whether they can serve their interests in a way that resorts to diplomacy, as opposed to force. >> the president said he is considering a number of diplomatic steps to isolate russia. on wall street, the dow fell in response to the tension in ukraine. >>> the trial of south african paralympic athlete oscar pistorius began. he shot and killed his girlfriend last year at his home. he said it was an accident, and he thought she was an intruder in the bathroom.